1. Field of the Invention
The present invention relates to a confocal microscope for obtaining information about a sample from a transmitted or reflected light from the sample.
2. Description of the Related Art
Confocal microscopes obtain information about a sample by illuminating the sample in the state of a spot, and by detecting with a photodetector the intensity of light transmitting through a confocal diaphragm aperture after gathering the transmitted or reflected light from the sample on the confocal diaphragm aperture. Moreover, the confocal microscopes can obtain information about a wide range of the sample by scanning the sample with various methods of spot light illumination.
FIG. 1 is a schematic diagram showing a confocal microscope of a laser scanning type as one example of conventional confocal microscopes.
The confocal microscope 50 shown in FIG. 1 is configured by comprising a laser light source 51, a PBS (Polarized Beam Splitter) 52, a two-dimensional optical scanner 53, a plurality of objective lenses 54, a ¼ λ plate 55, an image forming lens 56, a pinhole 57, a photodetector 58, a pinhole turret 59, a revolver 60, an XY stage 61, a Z stage 62, a computer 63, and a monitor 64.
Light emitted from the laser light source 51 is incident to the two-dimensional optical scanner 53 after transmitting through the PBS 52. The two-dimensional optical scanner 53 is composed of first and second optical scanners not shown. The two-dimensional optical scanner 53 two-dimensionally scans a light flux, and guides the light flux to any of the objective lenses 54. The light flux incident to the objective lens 54 is converged to scan the sample 65. At this time, the light that scans the sample 65 is converted from a linearly polarized light into a circularly polarized light when transmitting through the ¼λ plate 55. The light reflected on the surface of the sample 65 again transmits through the objective lens 54, is converted from the circularly polarized light into a linearly polarized light that is orthogonal to the incident light when transmitting through the ¼λ plate 55, reflected by the PBS 52 after being guided to the PBS 52 via the two-dimensional optical scanner 53, and gathered on the pinhole 57 by the image forming lens 56. Since the pinhole 57 is arranged at a position that is optically conjugate to the objective lens 54, only a focused light of the light reflected from the sample 65 transmits through the pinhole 57, and is detected by the photodetector 58. Within the pinhole turret 59, a plurality of pinholes having different diameters are arranged to be selectable. To the revolver 60, the plurality of objective lenses 54 are attached to be selectable. The sample 65 is placed on the XY stage 61, and can be moved by the Z stage 62 in the direction of an optical axis. Operations of the two-dimensional optical scanner 53, the Z stage 62, the photodetector 58, the pinhole turret 59, and the revolver 60 are controlled by the computer 63.
FIG. 2 is a schematic diagram showing a relationship between the relative positions Z of the objective lens 54 and the sample 65 and a signal I output from the photodetector 58. The relationship between the relative position Z of the objective lens and the sample and the signal I output from the photodetector is hereinafter referred to as an I-Z curve.
As shown in FIG. 2, if the sample 65 is placed at a focused position Z0 of the objective lens 54, the signal I output from the photodetector 58 is maximized. As the relative position Z of the objective lens 54 and the sample 65 is getting away from this position, the signal I output from the photodetector 58 rapidly drops.
With this characteristic, converged light is two-dimensionally scanned by the two-dimensional optical scanner 53, and the signal I output from the photodetector 58 is imaged in synchronization with the two-dimensional optical scanner 53, whereby only a particular height of the sample 65 is imaged, and an image (confocal image) acquired by optically slicing the sample 65 can be obtained. The obtained image (confocal image) is then displayed on the monitor 64. Moreover, the height information of the sample 65 can be obtained by acquiring a confocal image at each point of the sample 65, and by detecting the position of the Z stage 62, at which the signal I output from the photodetector 58 is maximized. Additionally, an image focused on all of planes (omnifocal image) can be obtained by superposing and displaying the maximum values of the signal I output from the photodetector 58 at respective points of the sample 65.
Additionally, an appropriate image required by a user can be obtained by selecting a suitable pinhole from the pinhole turret 59 in accordance with the performance of an objective lens 54 selectable with the revolver 60, the characteristic of the sample 65, or the like (For example, see Japanese Patent Publication No. 2007-133419).
Furthermore, there is a confocal microscope that varies the diameter of a pinhole in order to optimize a height measurement (for example, see Japanese Patent Publication No. 2005-55540).
Still further, there is a confocal microscope that obtains a difference between pieces of information obtained from pinholes by using the diameters of the plurality of pinholes, and obtains an image on the basis of the difference (for example, see Japanese Patent Application No. 2002-517774).
Still further, examples of a method for varying a pinhole include a variable pinhole mechanism that varies the size of a pinhole itself, and a method for arranging pinholes of different diameters respectively for a plurality of partitioned optical paths in addition to a turret mechanism.